.pan{
    width: 450px;
    height: 450px;
    display: flex;
    flex-wrap: wrap;
    align-content: flex-start;
    border:1px solid transparent;
    position: relative;
}
.top{
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 15px;
    background-color: rgb(143,173,183);
    z-index: 2;
    border-radius: 15px;
}
.left{
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    width: 15px;
    background-color: rgb(143,173,183);
    z-index: 2;
    border-radius: 15px;
}
.right{
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    width: 14px;
    background-color: rgb(143,173,183);
    z-index: 2;
    border-radius: 15px;
}
.bottom{
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 14px;
    background-color: rgb(143,173,183);
    z-index: 2;
    border-radius: 15px;
}